Acoustic sensor arrays protect soldiers by allowing for long range detection, tracking, and classification of enemy vehicles. An acoustic sensor array may consist of several sensors arranged in a circle which pick up acoustic data and use it to calculate the bearing angles to one or more targets. If two or more arrays are available, geometric triangulation may be used to pinpoint the location of the targets, and transmit this to a remote location via a transmitter. Currently, larger arrays must be manually installed by soldiers, while smaller arrays may be deployed by aircraft or artillery.
Smaller arrays, such as those where the sensors are arranged on a circle with a diameter of approximately fifteen centimeters or less, do not require installation by soldiers. However, they measure the bearing angle with an error having a standard deviation greater than four degrees. The magnitude of this error means the arrays must be placed close to the target to be accurate and effective.
Larger arrays, such as those where the sensors are arranged on a circle with diameter of approximately one meter or more, achieve greater accuracy because their size is closer to the acoustic wavelengths they are measuring, resulting in more accurate beamforming methods which are used to determine the bearing angles. These arrays can measure the bearing angle to a vehicular target 500 meters away with an error that has a standard deviation of less than one degree. Larger arrays, however, typically cannot be deployed from aircraft or by artillery. Therefore, they must be installed manually by soldiers, which jeopardizes the soldiers' safety.
While smaller arrays that can be deployed by aircraft or by artillery partially address the problem of protecting soldiers, they are an incomplete solution because their size limits their accuracy. In addition, achieving accuracy in the placement of an array is difficult when deploying them this way.
Therefore, it would be desirable to have a relatively large, airborne acoustic sensor array that does not require manual installation by soldiers. Such an array would be capable of autonomous deployment, lessening the endangerment of soldiers, while providing the greater accuracy of a larger array.